Well, this isn't the most elegant way to do it, but you could open your index page in your theme and find where the code is located that prints the categories, comments, etc. at the bottom of the post and add:

Naturally, you would need to have an image file called "hr_image.gif" in your images directory. That image file would then scroll across the screen, on the horizontal x-axis, and provide the look of what you want. Naturally, you would have to place the <hr /> tag in the appropriate place in the WordPress theme file.

I am using this technique to add the little "squiggly" thing between posts at:

Naturally, you would need to have an image file called "hr_image.gif" in your images directory. That image file would then scroll across the screen, on the horizontal x-axis, and provide the look of what you want. Naturally, you would have to place the <hr /> tag in the appropriate place in the WordPress theme file.

I am using this technique to add the little "squiggly" thing between posts at: